Genome-wide expression analysis at three fruit ripening stages for tomato genotypes differing in fruit shelf life

Abstract

The ripening stage at harvest time determines the tomato fruit quality. After the fruit achieves its maximum size several metabolic changes of typically climacteric fruits are produced. Two cultivated genotypes of Solanum lycopersicum (Caimanta and 804627), with normal and altered fruit ripening, respectively and two accession, LA1385 of S. lycopersicum var. cerasiforme and LA722 of S. pimpinellifolium, with genes that prolong fruit shelf life, were tested to: 1) characterize and make a comparatively analysis for the transcriptome at different fruit ripening stages in genotypes that differ in fruit shelf life by cDNA-AFLP; and 2) provide further insight into the relationship between the extreme phenotypic differences for ripening among the genotypes through changes at transcriptomic level. Fruits at the breaker stage (B) were evaluated for fruit weight, firmness and fruit shelf life. The elapsed days between mature green (MG) and breaker stages Days (MG-B) as well as the elapsed days between B and red ripe (RR) stages Days (B-RR) were recorded. Comparison among ripening stages showed a great polymorphism related to the changes in gene expression. For all genotypes the transition from B to RR stages had higher polymorphism than the transition from MG to B. It was observed a great genetic variability for the phenotypic traits in agreement with the changes of gene expression. Moreover, it was observed that the transcriptome expression profiles in the initial and intermediate stages during ripening (MG and B) are more important to characterize genotypes. The wild species which have long shelf life do not show as drastic changes in gene expression as the cultivar with altered ripening that carrythe nor gene. These results suggest that the expressed or silenced genes could be involved, in some way, in the determination of the phenotypic traits evaluated in this study.